Operation of an internal combustion engine, for example a diesel, gasoline, or gaseous fuel-powered engine, can cause the generation of undesirable emissions. These emissions, which may include particulates, oxides of nitrogen (NOx), and oxides of sulfur (SOx), are generated when fuel is combusted within a combustion chamber of the engine. If no emission reduction measures are in place, these undesirable emissions will eventually be exhausted to the environment.
Many different approaches, such as exhaust aftertreatments, have been developed to reduce the amount of emissions discharged during the operation of an engine. Some exhaust aftertreatments require periodic regeneration to prolong their use. Aftertreatment regeneration can require incremental fueling in the form of late post injections, which require additional capacity of the engine's fuel delivery system.
Historically, a single fuel transfer pump has been used to provide fuel for both the combustion within the engine and for aftertreatment regeneration. Although effective, the pressure and flow rate requirements for the engine combustion and the aftertreatment regeneration can vary drastically. Specifically, engine combustion requires a fuel flow of a relatively lower pressure and a relatively larger flow rate compared to aftertreatment regeneration. In order to meet the requirements of both systems, the operating conditions of the fuel transfer pump may be frequently switched between different states, for example, from a high-pressure state to a low-pressure state. Operating under these different conditions can cause early failure of the transfer pump and result in increased maintenance cost and lower efficiency.
One example of a single pump that can provide substantially different flows is described in U.S. Pat. No. 7,150,268 (the '268 patent) issued to Shafer et al. on Dec. 19, 2006. In particular, the '268 patent discloses a fuel pumping system having commonly housed first and second pumping elements, each configured to output a flow of fuel at a variable pressure and a variable flow rate. The flows from the first and second pumping elements are both directed to separate manifolds of an engine. While the fuel pumping system of the '268 patent may allow for variable fuel pumping to two separate locations, such a fuel pumping system may be overly complex and expensive.
The fuel delivery system of the present disclosure is directed toward improvements in the existing technology.